The purpose of this protocol is to evaluate the safety and biologic effect of repeat administration of the AdgvCFTR.10 vector to the epithelium of the large airways of individuals with cystic fibrosis. THe study is divided into 3 parts. Part A is an ascending single dose toxicity/gene expression study to define the pharmocodynamics of expression of the normal CFTR cDNA in the airway ephithelium following single dose administration of the vector to the airways. Part B is designed to evaluate toxicity/gene expression of repeat dosing at shorter intervals at the doses showing expression in Part A, while part C is designed to evaluate toxicity/gene expression of repeat dosing at a higher dose than that in Part A. In parts A and B, prior to administration of the vector, parameters for safety and expression will be evaluated in the baseline control period. In Part C, the baseline control for Part A will be used, since Part C represents an extension of the dosing in Part A. The vector will be administered three times in one lobe via a catheter via a fiberoptic bronchoscope in a volume of 100 microliters.